The present invention relates to a current monitoring system.
Referring to FIG. 1, many electrical power distribution systems include a power panel enclosure 10 into which is provided electrical power using one or more sets of wires 12. The electrical power may have any voltage, any current, and any number of phases (e.g., single phase, two phases, or three phases). Each phase of the electrical power to the power panel is normally provided to a separate bus bar 14a, 14b, and 14c, which are normally elongate conductors within the power panel 10. A plurality of circuit breakers 16a, 16b, 16c, etc., which trip or otherwise selectively disconnect electrical power, are electrically interconnected between one or more of the bus bars 14a, 14b, and 14c, and respective loads 18 external to the power panel 10. In many power panels 10 the circuit breakers 16 are vertically aligned in one or more strips 20 and 22. When the load 18 interconnected to a respective circuit breaker 16 within the power panel 10 draws excessive electrical current then the circuit break 16 trips or otherwise disconnects the electrical power to the load 18. In this manner, if a load shorts and thereafter draws excessive current then the circuit breaker will trip.
In a business or residential environment a set of electrical loads, such as motors, outlets, heaters, lights, machinery, instrumentation, etc., may be electrically interconnected to a single circuit. When the electrical current provided to the loads from a single circuit is excessive then the respective circuit breaker(s) will disconnect the electrical power to all of the loads. Initially, the anticipated current requirements for all of the loads interconnected to a single circuit breaker(s) may be added together to ensure that the total load will be sufficiently below the rating for the circuit breaker. In this manner, the circuit breaker will not inadvertently trip with normal variations in the current drawn by the loads. However, after the initial installation of the loads and a suitable circuit breaker for those loads, additional loads are frequently added to existing circuits without sufficient consideration of the total existing load for the respective circuit breaker(s). If excessive additional loads are added to the circuit breaker(s), then the circuit breaker(s) will have a tendency to trip during normal operation. While this may be generally acceptable in a residential environment, in a business environment the unanticipated tripping of the circuit breaker, especially when none of the loads are actually shorted, is simply unacceptable.
For example, in a computer server farm environment five circuit breakers may each be electrically interconnected to five computer servers, having a total of twenty-five computer servers. If three additional computer servers are added to the computer server farm, they may be electrically interconnected to the same circuit breaker. Frequently the installer is in a hurry to install the three additional computer servers to the network and interconnects the additional three computer servers to any readily available power outlet. However, having eight computer servers electrically interconnected to a single circuit breaker, which is properly sized for only five computer servers, will likely result in tripping the circuit breaker during normal usage. This may be simply unacceptable for operating a computer server farm where uninterrupted service is important. In many cases, the power provider to the server farm guarantees up time of the power provided to the computer servers. In the event that the power is interrupted, the power provider may be required to pay a substantial financial penalty.
Referring to FIG. 2, to monitor the current levels of individual circuit breakers 16 a respective current sensor 20 may be interconnected to the wire on the load side of the respective circuit breaker 16. The outputs 22 of each of the current sensors 20 may be interconnected to a current monitor 24 which signals an alarm condition if the output of one of the current sensors is to high. The current sensors 20 may be interconnected to one or more current monitors. It takes considerable time to install, at significant expense, all of the current sensors 20. In addition, because of the significant number of individual wires 22 an installer has a significant tendency to interconnect the wires 22 to improper places within the current monitor 24 and in particular to mismatch pairs of wires 22 from the same current sensor 20 rending the current sensors 20 ineffective. Moreover, it is problematic to ensure that the wires 22 indicated by the installer that relate to a particular current sensor 20 actually are interconnected to the desired current sensor 20. Typically, an installer likewise programs the current monitor 24 to indicate which wires attached to its interface are associated with which circuit breaker, and thus which load. Without proper attachment of the matched pairs of wires and attaching the wires in the proper location, any information that may be obtained may be simply nonsensical and relate to the wrong load (circuit breaker(s)), respectively. In summary, the potential installation problems are significant, especially when installed by untrained technicians.
What is desired, therefore, is an effective electrical measurement system.